In vivo evidence that L-S-nitrosocysteine may exert its vasodilator effects by interaction with thiol residues in the vasculature.

This study examined the effects of the lipophobic thiol chelator, para-hydroxymercurobenzoic acid (25 and 50 micromol/kg, i.v.) on the falls in mean arterial blood pressure and regional vascular resistances produced by L-S-nitrosocysteine (400 nmol/kg, i.v.) and the nitric oxide (NO)-donors, (Z)-1-&z. sfnc;N-methyl-N-[6(N-methylammoniohexyl)amino]&z.sfnc; diazen-1-ium-1, 2-diolate (MAHMA NONOate, 25 nmol/kg, i.v.) and sodium nitroprusside (10 microg/kg, i.v.), in urethane-anesthetized rats. The L-S-nitrosocysteine-induced responses were markedly diminished whereas the MAHMA NONOate- and sodium nitroprusside-induced responses were minimally affected by para-hydroxymercurobenzoic acid. These results suggest that the vasodilator actions of L-S-nitrosocysteine involves the interaction with membrane thiols in vascular smooth muscle of resistance arteries and that para-hydroxymercurobenzoic acid does not markedly affect NO-mediated vasodilation.